**Question:** True about case control study A/E

A. Case-control studies are used to establish cause and effect relationships
B. Case-control studies compare cases and controls to identify risk factors
C. Case-control studies are only useful for evaluating screening tests
D. Case-control studies are suitable for studying rare diseases

**Correct Answer:** B. Case-control studies compare cases and controls to identify risk factors

**Core Concept:** A case-control study is a research design used in epidemiology to investigate the association between exposure(s) and a specific disease or outcome. The study compares cases (individuals with the disease or condition) with controls (individuals without the disease or condition).

**Why the Correct Answer is Right:** In a case-control study, the primary objective is to identify risk factors and establish the association between exposures (factors that can lead to the disease) and the disease. By comparing cases and controls, researchers can determine the odds of exposure in cases compared to the controls. This helps to identify factors that increase the likelihood of developing a particular disease or experiencing a particular outcome.

**Why Each Wrong Option is Incorrect:**

A. False - Case-control studies are not used to establish cause and effect relationships. Cause-and-effect relationships are typically established through cohort studies, where individuals are followed over time and their exposures are assessed.

C. False - Case-control studies can be used to evaluate various research questions, including evaluating the effectiveness of screening tests, examining the prevalence of diseases, and identifying risk factors. However, they are not solely used for evaluating screening tests.

D. False - Case-control studies can be used to study diseases or conditions with low prevalence, as they are useful in investigating rare diseases or events. However, they are not limited to studying rare diseases alone.

**Clinical Pearl:** Understanding the purpose and design of case-control studies is essential for medical students, researchers, and clinicians. By comparing cases and controls, these studies can identify risk factors, prevalence, and effectiveness of interventions, while being particularly useful for studying rare diseases or events.